System and method for providing gyroscopic stabilization to a two-wheeled vehicle

ABSTRACT

This invention provides a stabilizing system and method for two-wheeled vehicles (typically small, human-powered bicycles) that affords the rider no restriction on the full range of movements (banks, leans, etc.) common to bicycles, but that provides greater stability during turns and other maneuvers so that an unintentional bank or tilt (potentially causing a fall) is less likely, even at relatively slow speeds and startup. A rotating mass of predetermined mass-value and radial mass-distribution is provided coaxially with the front axle. The mass is supported on bearings so as to freewheel with respect to the rotation of the front wheel. As such it can be induced to spin significantly faster than the front wheel thereby generating a gyroscopic effect at the front wheel about the axle. This gyroscopic effect influences the steering of the wheel by the rider. Due to precession, the wheel tends to follow any excessive bank by the bicycle, ensuring that the rider can “steer-out-of” an unintended tilt or bank. Likewise, the gyroscopic effect limits the rider&#39;s ability to execute excessive steering, thereby preventing jackknife movements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to stabilization systems for two-wheeled vehiclesand training devices for new riders of such vehicles.

2. Background Information

Learning to ride a bicycle, or similar human-powered vehicle, is one ofthe more difficult physical challenges faced by young children (and someolder ones). Children must develop awareness of what are, in essence,complex Newtonian principles of force-balance, gravity, torque, inertiaand momentum. Only by continually adjusting weight and balance for theprevailing velocity and turn radius can one proficiently ride a bicyclefor any distance. Starting a bicycle from a standing position is aparticular challenge as the forward velocity needed to maintain balancehas not yet been established. Likewise, turns are difficult for newriders as the weight and balance of the bicycle and rider shiftssuddenly and may become difficult to control. It is not uncommon for newriders to jackknife the bicycle wheel, causing both bike and rider totumble over.

The time-tested approach to preparing children to ride by exposing themto the basic dynamics of a bicycle is the use of training wheels.Briefly, training wheels are typically a pair small-diameter, hardrubber/plastic/wheels attached by removable brackets to the rear axle.When properly installed, the training wheels each extend outwardly (inan axial direction) from a respective axle end several inches, and aremounted so that their lowest points are slightly above the contact pointof the rear wheel with the ground. In this manner, the training wheelsallow the rider to lean slightly in either direction with one trainingwheel, or the other, engaging the ground to prevent the bicycle fortipping further.

While training wheels may be good first step for young riders, thetraditional ritual of removing them, and allowing the rider to ridetherewithout is often fraught with peril and scraped knees. Basically,the rider must now experience a new range of dynamics that were unknownwhile the training wheels were still attached. Generally, trainingwheels are inadequate because they do not simulate real, unrestrictedbicycle movement. They incorrectly teach riders to balance by relying onthe training wheels rather than actually learning to balance throughweight manipulation. Moreover, training wheels inhibit rider's frombanking as they turn, forcing them into bad habits. They rely on thetraining wheels, making the transition to autonomous riding extremelydifficult.

It is highly desirable to provide a training device that can be usedfollowing, or as a substitute to, training wheels that allows new ridersto experience the full range of dynamic forces associated with ridingwhile still providing a degree of safety during startup turns and slowriding. In particular, a device that enables children to ride stably atthe relatively slow speed of between 2.5 and 5 mph (common for most newriders) while still feeling the stability and behavior of a fastermoving bike (e.g. 10 mph+) is highly desirable.

SUMMARY OF THE INVENTION

This invention overcomes the disadvantages of the prior art by providinga stabilizing system and method for two-wheeled vehicles (typicallysmall, human-powered bicycles) that affords the rider no restriction onthe full range of movements (banks, leans, etc.) common to bicycles, butthat provides greater stability during turns and other maneuvers so thatan unintentional bank or tilt (potentially leading to a fall) is lesslikely, even at relatively slow speeds and startup. A rotating mass ofpredetermined mass-value and radial mass-distribution is provided (in anillustrative embodiment) coaxially with the front axle. The mass issupported on bearings so as to freewheel with respect to the rotation ofthe front wheel. As such it can be induced to spin significantly fasterthan the front wheel thereby generating a gyroscopic effect at the frontwheel about the axle. This gyroscopic effect influences the steering ofthe wheel by the rider. Due to precession, the wheel tends to follow anyexcessive bank by the bicycle, ensuring that the rider can“steer-out-of” an unintentional tilt. Likewise, the gyroscopic effectlimits the rider's ability to execute excessive steering, therebypreventing jackknife movements.

In an illustrative embodiment, mass is mounted on bearings that arethemselves mounted over the center hub of the bicycle wheel. The bicyclewheel is, in turn, mounted conventionally on a threaded axle that isattached to the front fork by opposing nuts. The mass of this embodimentis unpowered, and initially forced in to rotation by action of a helper(adult) as the rider starts the ride. It can be urged to rotate using avariety of permanently attached and/or detachable mechanisms. One suchmechanism employs a wrapped cord and a reel with a ratchet system thatlocks the reel in a cord-pulling direction and a spring that rewraps thecord in an opposite, cord-retracting direction. Alternatively, aremovable rack and mass-mounted pinion can be used to rotate to mass. Inanother alternative embodiment, the mass can be rotated using a drill orother cordless/corded electrical device having an elastomeric attachment(or gear) that engages an appropriate drive hub on the mass. Theattachment is inserted into contact with the hub for a small duration inwhich rotational motion is imparted to the drive hub from the electricaldevice. The device is then removed. The mass may rotate for a minute ormore given proper bearings and balance.

In another embodiment, the mass can be permanently and selectivelypowered using, for example, a motor assembly that is coaxial with thewheel hub. A battery or other power source can be attached to thevehicle to provide continuous power. Such a powered implementation maybe particularly suited for and adapted to disabled or older riders whorequire extra assistance. In addition, in alternate embodiments it isexpressly contemplated that the rotating mass (powered or unpowered) canbe provided non-coaxially within the structure of the steerable frontwheel. Appropriate mountings and/or spaces can be provided to allow thenon-coaxial mass to rotate appropriately free of interference from themoving wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, ofwhich:

FIG. 1 is a side view of a bicycle equipped with a stabilizing systemaccording to an illustrative embodiment of this invention;

FIG. 2 is a fragmentary side view of a front wheel for the bicycle ofFIG. 1 including the stabilizing system having a rotating mass accordingto one embodiment;

FIG. 2A is a fragmentary side view of a front wheel for the bicycle ofFIG. 1 including the stabilizing system having a rotating mass accordingto another embodiment;

FIG. 3 is a cross section of the wheel and rotating mass according toeither FIG. 2 or FIG. 2A;

FIG. 4 is a partially exposed perspective view of a cord-pull,recoil-type mechanism for initiating rotation of the mass according toan embodiment of this invention;

FIG. 5 is a fragmentary side view of an electrical device-drivenmechanism for initiating rotation of the mass according to anotherembodiment of this invention;

FIG. 5A is a fragmentary side view of the electrical device-drivenmechanism of FIG. 5 with an alternative drive hub design according toanother embodiment of this invention;

FIG. 6 is a schematic diagram showing the various rotations and axes ofinterest on a bicycle in connection with this invention;

FIG. 7 is a side view of a bicycle and rider in a starting positionemploying the system and method of this invention;

FIG. 8 is a front view of the bicycle and rider of FIG. 7 now in motion,and experiencing an imbalance;

FIG. 9 is a front view of the bicycle and rider of FIG. 7 in which theimbalance of FIG. 8 has induced an unintentional bank or tilt;

FIG. 10 is a front view of the bicycle and rider of FIG. 7 in which theunintentional bank or tilt of FIG. 9 is being compensated by precessionof the rotating mass to cause the rider to gently steer into the bank;

FIG. 11 is an on-angle view of the bicycle and rider of FIG. 7 showingthe recovery from the imbalance due to the steering of FIG. 10;

FIG. 12 is a graph comparing experimental data of upright travel(without rider) for the same bicycle with no rotating mass, a still massand a properly rotating mass; and

FIG. 13 is a graph comparing experimental data of travel path (with twodifferent riders) for the same bicycle with no rotating mass, and aproperly rotating mass.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A bicycle 100 having a stabilizing system according to an illustrativeembodiment of this invention is shown in FIG. 1. This bicycle isexemplary of a certain size and style of human-powered two-wheeledvehicle that is particularly adapted for smaller children. The terms“bicycle” and “vehicle” as used herein are expressly intended to referto any type of two-wheeled vehicle (including certain powered vehicles)that would benefit from the front-wheel gyroscopic stabilizing effect tobe described herein.

The bicycle 100 includes a conventionally mounted rear wheel assembly102, driven by a chain 104 that is, in turn operatively connected to apedal crank assembly 106. The bicycle frame 108 is constructed from aset of joined tubular members that support a seat 110 above the frame108 and is general alignment with the pedal crank assembly 106 so that arider (see below) can reach and operate the pedals with his or her feet.

The front of the frame 108 includes a down-tube with internal bearings(not shown) that rotatably supports a front fork assembly 122operatively connected to handlebars 124 of conventional design. On thelower end of the fork assembly 120, a front wheel 130 assembly isrotatably mounted. In this embodiment, the front wheel assembly 130includes an outer hub 132 upon which is mounted a tire (and innertube—not shown) 134. The outer hub 132 is supported radially and axiallywith respect to an inner hub 136 by a set of spokes 138. The inner hubis attached to the fork assembly's lower fork ends 140 as describedfurther below. The attachment allows the inner hub 136 to rotate freelyso that the bicycle can move in forward and reverse motion (forwardmotion being generally driven by the rear wheel assembly 102). Likewise,the handlebars rotate within a predetermined range (at least) about thesteering axis (dashed line SA) to allow the front wheel to turn withrespect to the frame.

Notably, the front wheel assembly 130 includes a rotating mass or“flywheel” assembly 160 mass according to an embodiment of thisinvention. With reference also to FIG. 2, the mass 160 is a circulardisk 162 having a width (described below) that is nested within andpasses freely between spokes 138 on each of opposing sides of the frontwheel assembly 130. The outside diameter DM of the mass disk 162 issmall than the inner diameter DOH of the outer hub 132. The differencebetween diameters is sufficient to allow the outside perimeter edge 210of the disk 162 to clear the convergence of the spokes 138 that joinalong the narrowed outer hub from each of opposing sides of the widerinner hub 136. In other words, the spokes generally define anequilateral triangle with the apex adjacent to the outer hub and thebase at the inner hub. Since the apex region is quite narrow, the radialheight of the disk should be short of the apex or any appreciablethickness in the disk will cause it to contact the spokes. However thedisk diameter DM can be increased to nearly that (diameter DOH) of theinner hub by making the disk thin, particularly near its outer perimeter210. Conversely, as will be discussed further below, it is desirable tomaintain the concentration of mass in the disk as far from the center(axis of disk rotation) to attain a high I value for the disk withoutrendering the disk overly heavy.

In order to accommodate a large-diameter disk, the outer hub 132 hasbeen modified to locate the tire fill stem 220 so as to project from theside of the hub 132, rather than the inner circumferential wall (asshown in phantom). Otherwise, the tire stem may contact the disk orsimply be rendered difficult to access to fill the tire. A variety oftire stem placements and shape are contemplated and should be within thecontemplation of those of ordinary skill whereby interference from thedisk can be avoided.

The center of the disk 162 includes a “drive hub” 230 according to anillustrative embodiment. The shape, size and underlying function of thedrive hub is highly variable. In this embodiment, the drive hub 230includes a pull-cord unit that allows the pull-cord to be rapidly paidout by grasping and drawing upon a cord handle 232 that projects fromthe side of the front wheel assembly. Upon pulling, a ratchet assembly(described further below) engages the disk as causes the disk to spin.The drive hub ratchet works in conjunction with a recoil unit thatwithdraws the cord after release. The ratchet allows free movementwithout engaging the disk in the withdrawal direction. It is expresslycontemplated that the drive hub can comprise a variety of mechanismsthat initiate a high-rpm spin-up of the disk.

FIG. 2A shows a wheel assembly 240 according to an alternate embodiment.As noted above, it is desirable the mass be concentrated along the outerperimeter of the wheel. Those of ordinary skill will recognize that thevalue for rotational moment of inertia (I, which equals mass m times thesquare of the radius, or I=mr²) is optimized where more mass isconcentrated at the outer perimeter of a rotating mass. Accordingly,FIG. 20 shows an embodiment of a rotating mass 250 with spokes, ratherthan a solid structure. The mass is concentrated in the outer perimeterregion 254. In this manner overall weight of the disk (and hence thefront of the bicycle) is reduced without substantially reducing I. Infurther embodiments, the mass can be concentrated in the perimeter of asolid disk by providing special weights (lead or steel billets forexample) in an otherwise lightened solid disk constructed from, forexample, aluminum or composite materials/polymers. Rotating masses neednot define a continuous circular perimeter. In alternate embodiments,weight can be distributed in the mass at the ends of a plurality ofseparated arms, so long as the arms or perimeter structure is wellbalanced with respect to the central axis so as to avoid up-and-downwobble as the mass rotates within a gravitational field. For thepurposes of this illustration, the first mass 162, shown in FIG. 2 canbe constructed of steel with a thickness of approximately one inch(highly variable), a diameter DM of 14-15.5 inches (highly variable) andan evenly distributed total mass of approximately 13.5 pounds. Theexample of FIG. 2A the mass 250 is also constructed of steel with athickness of about 1 inch. It also has an outer diameter DM ofapproximately 14-15.5 inches. In one experimental implementation, thetotal mass for this structure is approximately 12.3 pounds (a savings ofmore than a pound), and the I value is higher than the evenlydistributed disk. By using heavier materials in combination with lightercomposites the I-to-weight ratio for the mass can be optimized. In oneexample, the I value is in a general range of 210-240 pounds*in², but awider range of values for moment of inertia are expressly contemplated.

FIG. 3 shows a cross section of the central region of a wheel assemblyand mass 162 according to the embodiment of FIG. 2. The wheel assemblyis mounted on the bottom fork ends 140 by a pair of nuts 310, whichengage opposing ends of a threaded axle shaft 312. The axle shaft 312conventionally supports the inner hub 136 on bearings 320. Note that thestructure of the shaft 312 and inner hub 136 is highly variable. Themain object is to provide a wheel that rotates relative to the frontfork and a separate rotating mass that rotates freely with respect toboth the wheel and the front fork so that the mass can rotate at arelatively high RPM so as to generate a gyroscopic effect even when thefront wheel is barely moving or stationary. To accomplish this freerotation of the moving mass, the inner hub 136 has been divided into twopieces (or a plurality of sections) 324 and 326 with central break 330therebetween, over which is placed a cylindrical sleeve 332 that forms anew joint between the separated inner hub sections 324, 326. This jointmaintains the radial alignment of the sections 324, 326 and forms abearing surface for the mass. The sleeve 332 can be secured to theoutside of the hub sections 324, 326 using (for example) welds,fasteners adhesives or a press fit. The outer surface of the sleeve 332receives a bearing 340 that is pressed into the mass' drive hub 230. Thedrive hub can be constructed from any durable metal (aluminum alloy, forexample) or polymer/composite material. In this manner, the drive hub320 rotates freely on is bearing with respect to the sleeve 332, andhence, the front wheel. The drive hub is secured to the radially outwardportion 350 of the mass. This interconnection can be by press fit,fasteners, welds, adhesives or any other acceptable technique.Alternatively, the drive hub 230 and outer mass 350 can be formedunitarily from a single piece of formed, cast, molded, and/or machinedmaterial (with appropriate fillers, inserts and weights applied to thematerial where appropriate).

As shown clearly in FIG. 3, the drive hub includes a cylindricalextension 360 of reduced diameter with respect to the main drive hubportion 366 (that engages the outer mass 350). This extension 360supports a wrapped cord 362 with a tail end 364 that exits the hub andengages the pull handle 232 shown in FIG. 2 above. The firm withdrawalof the cord causes a rapid spin up of the drive hub. A well-balancedmass with a good bearing may spin at high RPM for several minutes. Inthis embodiment, a spin RPM of approximately 250-400 RPM is sufficientto provide stability as will be described below.

An optional spacer 370 is provided to at least one side of the sleeve332. This spacer assists in maintaining the drive hub axially centeredon the sleeve. Alternate centering and fixing mechanisms are expresslycontemplated. In addition, a conical or domed shield 376 is providedbetween the fork end 140 and spoke flange 370 as shown. While only oneside is shown having a shield, this shield can be applied to both sidesof the wheel assembly to protect the rider and others from thefast-rotating mass. The shield can be constructed from a durablepolymer, such as polycarbonate. It can be transparent/translucent andcan include various graphics and visual effects where appropriate.Likewise, the mass can be provided with graphical patterns that, inconjunction with the shield, may be used to create an entertainingeffect when in motion. The shield 368 includes a port 380 through whichthe cord end 364 passes. This allows the user to pull the cord 364 whilehis or her hands are protected from contact with the mass.

With reference now to FIG. 4, a recoiling, cord-pull drive hub assembly230 according to an illustrative embodiment of this invention is shownin further detail. It should be understood that the structure of thisassembly is only exemplary. Those of ordinary skill should be familiarwith this type of rotation-inducing mechanism as it is substantiallysimilar to those found in the pull starters of small engines. The drivehub 230 includes the above-described larger-diameter main portion 366and a smaller diameter projecting cylinder. This cylinder is actually anouter reel that rotates with respect to the main portion and a fixedlyattached inner ratchet base 420. The ratchet base includes a series ofradial grooves 430 that selectively engage spring loaded pawls attachedto the reel 410 when the cord end 364 is pulled outwardly (arrow 440).That is, the pawls 432 lock into the grooves 430 when the cord ispulled, causing the reel to rotate (curved arrow 444) and the mainportion 366 to also rotate (curved arrow 446). However, the reel 410includes a spring assembly 460 that is unwound by the pulling of thecord, and that rewinds to relieve tension, thereby drawing the cord backinto a wound position (dashed arrow 450). The pawls 432 disengage forthe ratchet bases 430 in this direction reverse to allow rewind to occur(dashed curved arrow 452). Likewise, the disengaged pawls allows thereel to be free from rotation while the mass spins at high speed (thus,no reverse dashed arrow on the main portion 366 is shown).

As noted above, the spin-up mechanism for the mass is widely variable.One alternate mechanism is shown in FIG. 5. Simply, the drive hub 510includes an extension 512 from the main portion 514 that isfrustoconical in shape. This allows firm engagement with a frustoconicaltip 516 of an electrically driven device, such as the illustratedcordless drill 518. The tip can be a hard rubber or other elastomer tofirmly engage the extension 512. By simply inserting the drill tip 516through a hole in the shield (described above), the tip contacts theextension 512 and spins it once power is applied. In practice, the tip516 can be provided as part of the kit a user receives with the bicycleand/or accessory wheel assembly of this invention.

FIG. 5A shows a slightly modified drive hub 550 with a main portion 554,in which the same frustoconical tip 516 (as FIG. 5) drives astraight-cylindrical extension 552. The corner 620 of the cylinder mayassist in providing engagement between the tip and extension. A varietyof tip shapes, extension shapes, materials and surface textures areexpressly contemplated.

Having described the structure of an exemplary system for gyroscopicallystabilizing a front wheel of a bicycle, the function of the system isnow described in further detail. Referring to FIG. 6, the dynamic forcesof interest are as follows:

Rotation of the wheels (curved arrows 610) translates into forwardvelocity along longitudinal axis 612 (when running with a straightenedfront wheel). Banking generally about the longitudinal axis (actuallyabout wheel-to-ground contact points) is shown as curved arrow 620. Thefront wheel steers (curved arrow 630) about the above-described steeringaxis SA.

The mass 160 rotates about the front wheel axis 650, thereby generatinga characteristic angular momentum L (where L=Iω, in which ω is theangular velocity of the rotating mass). The banking rotation representsa torque τ generally about the longitudinal axis 612. Where angularmomentum and torque cross, a precession is generated. This precession isthe property whereby a gyroscope rotates at a predetermined magnitude inresponse to crossed forces. In this case the precession Ω_(P) ischaracterized by the equation:τ=Ω_(P) ×L.

In other words, the equation governing precession is derived from thefact that torque equals the angular velocity of precession crossed withthe angular momentum. Hence, a torque on a gyroscope (such as the torquefrom a child falling in an excessive or unintentional bank or tilt aboutthe longitudinal axis) is transferred 90 degrees, and results inprecession. For example, if the child were to tip to the right, thewheel would simply turn to the right. This allows the weight of thechild to be re-centered over the front wheel. It is particularly desiredthat precession (Ω_(P)) be small in order so as to produce a relativelysmooth recovery for the bicycle wheel. Since precession is inverselyproportional to angular momentum a large I value, produces a relativelysmall precession for a given applied torque.

Reference is now made to the exemplary rider-training session of FIGS.7-11. The process begins with the rider 710 seated atop the bicycle 100,grasping the handlebars 124 in forward-steering position, with feet 712prepared to begin pedaling. The helper places a grasping hand 720 on thepull-cord handle 232 and rapidly draws it (arrow 722) to spin the mass160. After spin-up, the rider 710 begins to pedal.

In FIG. 8, the rider 710 experiences and imbalance (arrow 810) that maylead to an unintentional/undesired bank or tilt. This bank occurs inFIG. 9, in which the bicycle leans (arrow 910) over, threatening toeject the rider 710.

As shown in FIG. 10, due to the precession generated by the spinningmass 160, the front wheel 130 turns smoothly (arrow 1010) in thedirection of the unintentional bank, causing the handlebars 124 to befirmly urged to “steer-into” the bank. Thus the rider 710 experiences aturn that causes the bicycle 100 to begin to right itself (arrow 1020).Finally, in FIG. 11, the turn, induced by the imbalance and bank iscomplete and the rider 710 is riding vertically again in a newdirection. The act of banking the bicycle has lead to a conventionalturn, without jackknifing the bicycle or causing it to tip over, thusemulating a natural motion of banking and turning, even at relativelylow speeds. This allows the young, slowly moving rider to learn thedynamics associated with faster riding, while maintaining a slower,safer speed.

To further prove the effectiveness of the stabilizing system of thisinvention a series of tests were performed with the approximate resultsshown in FIG. 12. A bicycle was launched, riderless (e.g. a “ghost”test) along a relatively flat path by hand at a relatively slow speed.Data bars for a non-moving mass (1210) show an upright time duration(before falling over) of approximately 1.2-2.2 seconds. Results areroughly similar for a bicycle with no mass installed (1220). Conversely,a bicycle with a mass moving at 200-400 RPM (1230) shows markedlyincreased upright time of approximately 2.3-6 seconds, with most timesfalling into the 4-5 second range (more than double the non-stabilizedtimes).

Similarly, FIG. 13 shows comparative graphs 1310 and 1320, 1330 and 1340for two respective test subjects, both relatively inexperienced juvenileriders. The graphs show the length of path traveled versus diversionfrom a straight path (both in feet). In both cases the graph for thebicycle without spinning mass (1310 and 1330) displays a higheramplitude from a straight line than the graphs for the bicycle withproperly spinning mass (1320 and 1340).

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope thereof. By way ofexample, while a wheel having a plurality of radial thin metal spokes isemployed, a variety of wheel and hub structures can be employed. Forexample, a hub comprising a pair of clamshell halves that is assembledaround the disk can be employed in an alternate embodiment, such a hubcab have outer surfaces that act both as a shield for the disk and theradial load-bearing member between the inner and outer hubs. Similarly,solid spokes with appropriate grooves for nesting the disk can be used.A variety of other improvements and modifications to the wheel, disk ordrive hub can be implemented within the spirit and scope of thisinvention. Finally, while the exemplary embodiment described herein hasbeen applied to a bicycle suitable for small children, it is expresslycontemplated that this stabilizing system can be applied to thesteerable front wheels of a variety of two-wheeled vehicles. Inalternate embodiments it can be applied to adult-sized vehicles, and canbe continuously powered by electric motor, or the like. This device canalternatively be applied to powered two-wheeled vehicles, such asmopeds, motorcycles and scooters to provide further stability and/or actas a training tool. Such an application can be continuously ormomentarily powered as appropriate. In addition, in alternateembodiments it is expressly contemplated that the rotating mass (poweredor unpowered) can be provided non-coaxially within the structure of thesteerable front wheel. Appropriate mountings and/or spaces can beprovided to allow the non-coaxial mass to rotate appropriately free ofinterference from the moving wheel. Accordingly, this description ismeant to be taken only by way of example, and not to otherwise limit thescope of this invention.

1. A system for stabilizing a two-wheeled vehicle comprising: a movingmass mounted with respect to a steerable front wheel of the vehicle thathas a characteristic precession so that the front wheel is urged in adirection of an unintentional bank to provide recovery in the form ofsteering from the bank.
 2. The system as set forth in claim 1 whereinthe moving mass comprises a disk mounted on a bearing structure coaxialwith an inner hub of the front wheel.
 3. The system as set forth inclaim 2 wherein the front wheel is a bicycle front wheel mounted on asteerable fork operatively connected to handlebars.
 4. The system as setforth in claim 3 wherein the disk comprises a structure having massconcentrated adjacent to an outer perimeter thereof.
 5. The system asset forth in claim 3 wherein the mass includes a drive hub locatedadjacent to the inner hub and including an interface adapted to causethe mass to freely spin at for a desired time interval about the innerhub.
 6. The system as set forth in claim 5 wherein the drive hubincludes a pull cord that spins the hub by action of pulling and arecoil winding reel to draw the cord after pulling.
 7. The system as setforth in claim 5 wherein the drive hub is constructed and arranged toengage an electrically operated tip that causes the drive hub to spin inresponse to engagement by and rotation of the tip.
 8. The system as setforth in claim 1 wherein the front wheel includes a shield thatrestricts access to the mass.
 9. The system as set forth in claim 8wherein the shield includes a port through which a mechanism that spinsthe mass is passed.
 10. A method for stabilizing a two wheeled vehicle,at least during start of vehicle motion comprising the steps of:initiating rotation of a rotating mass mounted with respect to asteerable front wheel of the vehicle; while mounted on the vehicle,initiating forward motion using a mechanism that rotates a rear wheel ofthe vehicle; and responding to precession induced in the front wheel bymotion so as to reduce unintended tilting of the vehicle.
 11. The methodas set forth in claim 10 wherein the step of initiating rotationcomprises applying to the rotating mass, and then withdrawing from therotating mass, a rotating, electrically operated mechanism.
 12. Themethod as set forth in claim 10 wherein the step of initiating rotationcomprises causing the rotating mass to rotate on a mounting coaxial withan axle of the front wheel that allows the rotating mass to freewheelwith respect to the front wheel.